1. Field of the Invention
The present invention relates generally to magnetic disk drives with load/unload ramps and, more particularly, to a load/unload ramp structure having a plurality of ramps.
2. Description of the Background Art
A magnetic disk drive storage device typically comprises one or more thin film magnetic disks, each having at least one data recording surface including a plurality of concentric tracks of magnetically stored data, a spindle motor and spindle motor controller for supporting and rotating the disk(s) at a selected RPM, at least one read/write transducer or "head" per recording surface formed on a slider for reading information from and writing information to the recording surface, a data channel for processing the data read/written, a positionable actuator assembly for supporting the transducer in close proximity to a desired data track, and a servo system for controlling movement of the actuator assembly to position the transducer(s) over the desired track(s).
Each slider is attached on one surface to an actuator arm via a flexible suspension and includes on an opposite side an air bearing surface (ABS) of a desired configuration to provide favorable fly height characteristics. In contact start/stop disk drive designs, the slider and transducer are only in contact with the recording surface when the spindle motor is powered down. As the disk begins to rotate, an air flow is generated which enters the slider's leading edge and flows in the direction of its trailing edge. The air flow generates a positive pressure on the ABS, lifting the slider above the recording surface. As the spindle motor reaches operating RPM, the slider is maintained at a nominal fly height over the recording surface by a cushion of air. Then at spin-down, fly height drops until the slider is once again in contact with the disk.
Because contact start/stop recording subjects the slider and transducer to extensive wear, some disk drive designs alternatively employ "load/unload" technology. According to this design, a ramp is provided for each slider/suspension assembly at the inner or outer diameter of the disk where the slider is "parked" securely while the spindle motor is powered down. During normal operation, the disk speed is allowed to reach a selected RPM (which may be below the normal operating RPM) before the head is "loaded" onto the disk from the ramp on the air cushion generated by the disk's rotation. In this manner, the slider flies over the disk without significant contact with the disk surface, eliminating contact start/stop wear. The load/unload ramp structure is generally made of plastic which can be injection molded into complex ramp structures.
By far, the most challenging mechanical aspect of load/unload is obtaining and maintaining the desired vertical clearance between the ramp surfaces and the disks. Packaging considerations demand as tight a clearance as possible for the load/unload structure, given the limited fixed form factor dimension and the many items competing for space in the disk drive, including disks, base plate, actuator, and electronics. Additionally, alignment of the ramp to the actuator suspensions is also extremely critical. Therefore, designing a ramp system which requires little additional clearance for tolerance/variability due to the installation of the ramp is of great importance.
Current load/unload art utilizes the base of the ramp to establish the vertical relationship to the disk pack. The ramp base is secured tightly to the base plate to establish the vertical positioning of the load/unload structure and the vertical clearance between individual ramp surfaces and the disks. While this approach may be suitable for shorter load/unload structures having only a couple of ramps, problems occur with taller load/unload structures having a large number of ramps (e.g., 5-10 ramps). First, due to the space constraints on the base plate of the disk drive, the dimensions of the surface of the ramp base for attachment to the base plate are small compared to the height of the load/unload structure, resulting in a long cantilever structure. When the base of the load/unload structure is screwed into the base plate of the disk drive, minor deformations caused by tightening of the screw or minor imperfections in the surface of the base plate or the base of the load/unload structure can cause the angle of the cantilever structure to be offset from perpendicular to the base plate (i.e., tilted), thereby altering the vertical clearance between the ramp surfaces and the disks. Therefore, there is a need in the art for a load/unload structure which can be accurately positioned so that the structure is perpendicular to the base plate of the disk drive.
It is the object of the present invention to provide a load/unload structure having improved perpendicularity to the base plate of the disk drive. Other objects and advantages will be apparent from the following disclosure.